EXCESSIVE RAINS 



43 



bola used formerly.* These two lines meet at a point of the 

 diagram representing a duration of one hour and an intensity 

 of .87 inch. The line to the left of the point of intersection 

 is quite steep, while that on the right is more nearly horizontal. 

 The combination shows very clearly that the maximum intensity 

 of the rainfall diminishes rapidly as the duration increases from 

 a few minutes to an hour, and that for rains of uniform intensity 

 lasting more than one hour the rate of diminution is quite 



RELATION BETWEEN 



INTENSITY AND DURATION 



OF VARIOUS STORMS 



CHESTNUT HILL RESERVOIR, 

 BOSTON 

 1879-1901 



1 2 



Duration of Storm in Hours 



FiG. 7. 



slow. By getting the equations of the two enveloping lines, he 

 has for storms of less than one hour ^ = 3.730.05060:, and 

 for those over one and less than five hours the relation 

 y = o.ggo.oo2x. Repeating the work for Rochester alone, 

 he gets ;y = 2. 10 0.02053;. Kuichling distinctly states that 

 no great accuracy can be claimed for this formula, nor can he 

 recommend it for general use, despite its great value in the 



* See Trans. Am. Soc. C. E., Vol. XX, p. i. 



